1. Field of Invention
When surfaces such as concrete, brick, masonry, stone, etc. are applied with waterproofing sealer compositions, they get overall protection from corrosion and general deterioration. The treatment reduces the rate of water absorption considerably, thereby preventing water related damages. There are many sealers/repellents known to the prior art. For example, acrylics, vinyls, silanes, silicones, polyurethanes, styrene-butadiene copolymers, silicates, siloxanes, siliconates etc. They are either water based or solvent based or water-solvent based.
Due to fire hazard and environmental risks associated with many known solvents, it is advantageous to use effective water based waterproofing compositions. Waterproofing sealer/repellents based on .dbd.Si.dbd. chemistry play a significant role in the field of waterproofing materials. There are three popular groups of silicone based materials being used as waterproofing materials namely 1. silicates, 2. silane, siloxane, siliconate and 3. silicones.
Silicates provide waterproofing properties by filling the pore structure of building materials with silicone dioxide precipitation.
Silanes, siloxanes and siliconates provide waterproofing properties by bonding with the substrate and thus offer a long lasting solution.
Silicones are present in the polymer form and they do not form chemical bonds with the substrate. They provide waterproofing properties by forming a non-bonded film.
2. Prior Art
Representative references which illustrate some of the prior art waterproofing compositions are described in the following U.S. Patents:
U.S. Pat. No. 3,772,065 to Seiler relates to alkyltrialkoxysilane solution in alcohol having up to two alkoxygroups per silicone atom for masonry applications.
U.S. Pat. No. 3,819,400 to Plankl et al. relates to a waterproofing material treated with a silane or a siloxane.
U.S. Pat. No. 3,879,206 to Nestler et al. relates to formulation containing alkyltrialkoxysilane and an organo functional silane for masonry applications.
U.S. Pat. No. 3,980,597 to Shihadeh relates to a composition containing polyurethane and neutralised bituminous material for roof waterproofing applications.
U.S. Pat. No. 4,341,560 to Saito et al. relates to a composition containing alkaline metal alkylsilioonates or phenylsiliconates along with calcium hydroxide or calcium oxide to waterproof gypsum.
U.S. Pat. No. 4,536,534 to Singer et al. relates to an aqueous primer based on alkali soluble acrylic resins and siliconates for application on strong alkaline substrate to bring about good water repellance and binding.
U.S. Pat. No. 4,814,407 to Canova et al. relates to a composition of an alkylalkoxysilane or a fluoroalkylalkoxysilane for improving resistance to absorption of water by a porous substrate.
U.S. Pat. No. 4,816,506 to Gamon et al. relates to an aqueous silicone dispersions containing polydiorganosiloxanes, organometallic compounds, siliconate and optionally a silicone resin for elastomeric coating or sealant applications.
U.S. Pat. No. 4,894,405 to Barron relates to a composition containing polyurethane and organosilane for concrete and masonry waterproofing applications.
U.S. Pat. No. 4,897,291 to Kim relates to a sealant composition containing polymeric binder, a wax hydrophobic filler and a water soluble alkalimetalsiliconate salt for sealing wood products against moisture absorption.
Siliconates are water soluble and they impart water repellency on porous surfaces. As per the conventional method of application, 30% by weight of siliconate solution is diluted to less than about 3% by weight. Dilution reduces solution viscosity and increases its penetration along the depth of the substrate.
However, there is a drawback in using diluted alkalimetal alkyl siliconate solution for waterproofing applications. When this solution is applied by brush/spray/roller to the substrate, siliconates react with carbon dioxide and carbonatious matters present in the substrate to form a water repellent, water-insoluble, white colored precipitate. This white layer may become quite visible;
1. on surfaces applied with excess waterproofing solution, PA1 2. on less porous surfaces, and PA1 3. on surfaces that require preservation of their external appearance and character e.g. facades, decorative tiles, colored stones etc. PA1 about 1 to 3 parts by wt. of water soluble alkalimetalalkyl siliconates PA1 about 0.2 to 10 parts by wt. of polymers(resins) PA1 about 0 to 0.5 parts by wt. of alkali silicates PA1 about 0.005 to 2 parts by wt. of additives PA1 about 0 to 20 parts by wt. of diluents PA1 the balance parts by wt. of water PA1 about 1.4 to 1.9 parts by wt. of water soluble alkali-alkyl siliconates PA1 about 1 to 3.5 parts by wt. of polymers PA1 about 0.001 to 0.2 parts by wt. of alkali silicates PA1 about 0.005 to 2.0 parts by wt. of additives PA1 about 0 to 5 parts by wt. of diluents PA1 the balance parts by wt. of water PA1 an ability to overcome the drawback related to the formation of a white precipitate on substrate surface. PA1 an ability to improve resistance to water absorption in porous surfaces such as concrete, brick, masonry, stones and others.
Such a change in discoloration and appearance of the substrate after curing of siliconate waterproofing solution is generally not acceptable from the aesthetic point of view.
Less than 1% by weight of siliconate solution minimizes formation of white residue to some extent but it gives a very poor waterproofing property.
The object of the invention is to overcome this drawback.